EP0476845B1 - Radiolumineszierende Lichtquellen - Google Patents

Radiolumineszierende Lichtquellen Download PDF

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Publication number
EP0476845B1
EP0476845B1 EP91307708A EP91307708A EP0476845B1 EP 0476845 B1 EP0476845 B1 EP 0476845B1 EP 91307708 A EP91307708 A EP 91307708A EP 91307708 A EP91307708 A EP 91307708A EP 0476845 B1 EP0476845 B1 EP 0476845B1
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EP
European Patent Office
Prior art keywords
radioluminescent
light
light source
matrix
radioactive element
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Expired - Lifetime
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EP91307708A
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English (en)
French (fr)
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EP0476845A1 (de
Inventor
Nazir P. Kherani
Stefan Zukotynski
Walter T. Shmayda
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Ontario Hydro
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Ontario Hydro
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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21H—OBTAINING ENERGY FROM RADIOACTIVE SOURCES; APPLICATIONS OF RADIATION FROM RADIOACTIVE SOURCES, NOT OTHERWISE PROVIDED FOR; UTILISING COSMIC RADIATION
    • G21H3/00—Arrangements for direct conversion of radiation energy from radioactive sources into forms of energy other than electric energy, e.g. into light or mechanic energy
    • G21H3/02—Arrangements for direct conversion of radiation energy from radioactive sources into forms of energy other than electric energy, e.g. into light or mechanic energy in which material is excited to luminesce by the radiation

Definitions

  • This invention relates to radioluminescent light sources and is particularly concerned with radioluminescent light sources which are powered by tritium.
  • the invention is also applicable to radioluminescent light sources in which a radioactive element other than tritium is used as a source of electrons or other subatomic particles for excitation of a phosphor.
  • Radioluminescence pertains to the generation of light by the excitation of a phosphor, more particularly from a radioactive source.
  • the first application of radioluminescence was to luminous paints to be used on watches, clocks, aircraft dials and the like, the paints incorporating an intimate mixture of radium and a zinc sulphide phosphor.
  • radionuclides such as promethium-147, krypton-85 and tritium
  • radioluminescent lights used for maintenance-free illumination, are mainly powered by tritium. Examples of the use of tritium in applications of radioluminescence are to be found, for example, in United States Patents Nos. 3,176,132, 3,260,846, 3,478,209 and 4,677,008.
  • tritium light sources were in the nature of radioluminescent paints, tritium being substituted for hydrogen in an organic resin used also as a binder to couple it with a zinc sulphide phosphor. Such light sources were inefficient, however, on account of the opacity of the resin and also the tendency to desorption of the tritium out of the resin. Subsequently, the most commonly used tritium light sources took the form of phosphor coated glass tubes filled with tritium gas. While these light sources are generally superior to the radioluminescent paints, both in ease of fabrication and in the more efficient use of tritium decay betas, they have their shortcomings.
  • radioluminescence is limited to only a few applications.
  • the limitation on the use of radioluminescence in many applications in which such use would be desirable is due to a failure to address two fundamental problems, namely (i) how to transmit the decay betas to the phosphorescent medium with negligible loss of energy, and (ii) how to convert the beta energy to light with minimum self-absorption by the phosphor.
  • an intrinsic radioluminescent source comprising essentially a radioactive element entrapped within an amorphous semiconductor matrix.
  • the amorphous semiconductor may be in the form of a thin transparent film deposited on a transparent substrate or alternatively upon a substrate providing a reflecting surface configured to concentrate the generated light and direct it in a desired direction.
  • the amorphous semiconductor matrix containing the radioactive element may be used as an electron source to excite a deposited phosphor layer.
  • the radioactive element may be tritium.
  • the amorphous semiconductor matrix may be for example, an amorphous silicon-tritium alloy (a-Si:T) produced by glow discharge decomposition of tritiated silane (SiT4) in a d.c. saddle field.
  • a-Si:T amorphous silicon-tritium alloy
  • SiT4 glow discharge decomposition of tritiated silane
  • suitable dopants or by alloying with elements, such as germanium, carbon and/or nitrogen, the colour or wavelength range of the resultant light can be tailored to suit requirements.
  • a radioactive element other than tritium for example C14 entrapped in the amorphous semiconductor matrix, may serve as the excitation source.
  • the present invention is based essentially on the use of thin films of tritium-occluded amorphous semiconductor, (herein referred to as TAS films,) deposited on suitable substrates which are themselves transparent to appropriate wavelengths, or which provide highly reflective surfaces on which the films are deposited.
  • TAS films can be deposited using one of several commercially available techniques; for example, by glow discharge decomposition of precursor gases to produce semiconductor materials. Tritium decay betas with a mean energy of 5.7 keV will traverse through a TAS film losing energy to the formation of electron-hole pairs and Bremstrahlung radiation until they are thermalized and combine with positive charges.
  • the preferred TAS is tritiated amorphous silicon (a-Si:T).
  • a-Si:T hydrogenated amorphous silicon
  • a-Si:H hydrogenated amorphous silicon
  • the interatomic bonding in a-Si is similar to that of crystalline Si.
  • the ranges of allowed energy states are similarly distributed in the two materials.
  • crystalline silicon is an indirect gap material in the Bloch function representation. It is this direct gap behaviour of a-Si that places it in the group of optoelectronic materials, together with GaAs.
  • A-Si:H can be deposited in the form of large area thin films onto a wide variety of low-cost substrates, such as glass, using low-temperature processing techniques (typically below 350°C). This makes a-Si:H the ideal candidate for many large surface area device applications.
  • low-temperature processing techniques typically below 350°C.
  • SiH4 silane
  • a process based on the principle of an electrostatic field supported charged particle oscillator, involves the use of glow discharge decomposition of silane in a d.c. saddle field. This process combines many of the positive attributes of both r.f. and d.c. diode discharge techniques.
  • the electrode configuration consists of an anode in the form of a stainless steel annular ring supporting a loosely woven stainless steel wire grid held by an insulating support between two additional stainless steel annular rings, of the same diameter, strung with similar stainless steel wire grids.
  • the two outside rings are grounded, and thus form the cathodes of a symmetrical saddle field cavity.
  • the heated substrate holders are mounted next to the cathodes. They may be raised to a positive or negative potential.
  • Silane, silane with phosphine, silane with diborane, methane, hydrogen, nitrogen and argon are admitted into the chamber through a multi-channel mass flow controlled manifold. Co-evaporation with silicon or dopants and alloying elements can be performed.
  • the d.c. saddle field electrode configuration facilitates discharge formation over a wide range of pressures, from over 500mTorr down to a few mTorr and even lower, while avoiding the tuning problems that plague the conventional r.f. techniques. Film growth in the r.f. discharges is largely controlled indirectly by the induced d.c. field.
  • the d.c. saddle field electrode configuration provides a similar d.c. potential distribution, but with direct controllability.
  • A-Si:H films that are mechanically stable, free of flaking or blistering, with good adherence to the substrate, can be simultaneously deposited onto both conducting and insulating substrates, using a discharge in silane, ignited in a d.c. saddle field plasma chamber.
  • the high discharge current that can be obtained, using a saddle field electrode configuration at relatively low pressures in order to minimize polymerization effects, allows for the deposition of semiconductor quality a-Si:H films at relatively high rates, in excess of 5 A/sec, as compared to about 2 to 3 A/sec using prior technology.
  • films have been produced with photoconductive gains of 2x104 at AM1 illumination, and dark resistivities of 5x1010 ⁇ cm.
  • Hydrogen incorporation can be controlled through the deposition conditions. For example, at a given deposition temperature, the relative fraction of hydrogen incorporated into monohydride and dihydride sites can be varied via the discharge voltage and pressure; higher voltages (i.e. higher than 1000 V), and lower pressures (i.e.less than 50 mTorr), enhance the incorporation of hydrogen into dihydride sites, particularly at low substrate temperatures (i.e. T s ⁇ 300°C).
  • A-Si:H exhibits very strong photoluminescence at temperatures below 150 K and still significant luminescence at room temperature. Electroluminescence has been observed in a-Si:H p-i-n diodes. The peak luminescence of a-Si-H lies in the infrared, at about 1.3 eV. However by alloying with carbon or nitrogen the energy gap of amorphous silicon can be increased to over 4 eV, and this way the electroluminescent peak can be moved into the visible part of the spectrum. Indeed, recently emission throughout the entire visible spectrum has been reported for a-Si:C:H p-i-n diodes (maximum luminance of 30 cd/m2 and efficiency of 10 ⁇ 4 lm/W at room temperature).
  • tritiated amorphous silicon (a-Si:T) films can be formed on a substrate, or films of related alloys involving silicon carbide and silicon nitride may be formed.
  • the material of the substrate may be glass, sapphire, quartz etc.
  • FIG. 1 shows a TAS film 10 of a few microns in thickness deposited on a substrate 11 of glass, quartz or sapphire.
  • the substrate is in the form of a plate about 1 mm thick.
  • the film 10 is substantially transparent to the light which is produced, the light being radiated in all directions as indicated by arrows.
  • This device representing the invention in its simplest form, is encased in a sealed transparent casing 12.
  • the TAS film has a uniformly distributed concentration of tritium, and therefore at the external surfaces of the film there will be a flux of primary and secondary electrons.
  • the TAS film is an electron source of total current of the order of nAcm ⁇ 2. From the point of view of light production a TAS film with a graded tritium concentration will tend to convert this extra energy to light and so increase the luminous exitance.
  • Figure 2 shows such a light source, similar to that in Figure 1, but having a graded tritium concentration which diminishes towards its surfaces, as indicated by the graph of Figure 2a.
  • the luminous flux can be further increased by providing an optically reflective film 13 between the TAS film 10 and the substrate.
  • the reflective film 13 which is of the order of 100 A in thickness, may be formed by depositing silver, for example, onto the substrate, the TAS film 10 being deposited onto the reflective film.
  • the TAS film preferably has a graded concentration of occluded tritium as in the case of the embodiment shown in Figure 2. The produced light which initially travels towards the reflective layer will tend to undergo specular or diffuse reflection, depending on the quality of the reflective film, and thus enhance the luminous exitance, ideally by a factor of two.
  • the luminous flux can be further increased by covering all the external surfaces of the graded TAS film 10 with an optically highly reflective film 14 save at one narrow edge.
  • light is concentrated by virtue of total internal reflection, thus giving rise to enhanced luminous exitance at said uncovered narrow edge 15.
  • the optically reflective coating must have an index of refraction which is less than that of the graded TAS film.
  • the total light output can be increased by depositing a very large number of alternating layers of optically reflective film 14 and TAS film 10.
  • Figures 5 and 6 is a greatly enlarged fragmentary view showing the film structure in cross section, the transparent casing being omitted to show the internal structure.
  • Figure 7 shows in perspective a light source having the same multilayer structure as the preceding embodiment of the invention, but of cylindrical configuration.
  • Figure 8 shows the multilayer structure of the light source in cross section, but with the thicknesses of the reflective and TAS films being greatly exaggerated for clarity.
  • the light sources described above may be referred to as "intrinsic" light sources, by which is meant that the tritium is occluded within the phosphorescent matrix. No external phosphor is required. In general such an intrinsic light source may be expected to produce a greater luminous exitance than an extrinsic light source. Nevertheless, the availability of a TAS film as an electron source, as previously mentioned in connection with Figure 1, permits the invention to be applied to an extrinsic light source, given the availability of a phosphor having sufficient quantum efficiency, stability against radiation damage, and desired emission characteristics. Figures 9 to 12 illustrate such extrinsic light sources.
  • the TAS film 10 is "sandwiched" between phosphor films 16 thereby yielding two planar surfaces emitting radioluminescent light.
  • the substrate 11, of glass, quartz or sapphire on which the phosphor is deposited is transparent to the light radiation emitted.
  • an optically highly reflective film 14 is deposited between the substrate 11 and the phosphor 16 so as to reflect the light and thereby enhance the luminous exitance, ideally by a factor of two.
  • the phosphor and TAS films are transparent and non-absorbing to the light radiation emitted.
  • the extrinsic light source is covered by optically highly reflective film 14 except at one narrow edge 15 so as to concentrate the light by total internal reflection and thus increase the luminous exitance.
  • FIG. 12 shows schematically, in enlarged section, a structure comprising very many extrinsic light source elements with enhanced luminous exitance stacked together to form a composite radioluminescent source with a large total light output.
  • the radioluminescent light sources are based on the use of thin films of tritium-occluded amorphous semiconductor.
  • other radioactive elements which emit decay betas may be used instead of tritium.
  • the matrix can most conveniently be deposited as a thin film,it will readily be understood that the matrix may comprise a body of substantial thickness so long as it is transparent to the light emitted by the recombination of the electron-hole pairs.
  • the usefulness of the embodiments shown in Figures 4 to 8, and Figures 11 and 12, in which light is transmitted within the film through a distance far exceeding the film thickness depends upon the matrix being essentially transparent regardless of its thickness.

Claims (11)

  1. Radiolumineszierende Lichtquelle mit einem radioaktiven Element, das in einer amorphen Halbleitermatrix (10) eingeschlossen ist.
  2. Radiolumineszierende Lichtquelle nach Anspruch 1, bei der das radioaktive Element ein beta-strahlendes Element ist.
  3. Radiolumineszierende Quelle nach Anspruch 1, bei der das radioaktive Element Tritium ist.
  4. Radiolumineszierende Quelle nach Anspruch 3, bei der die Matrix (10) amorphes Silizium ist.
  5. Radiolumineszierende Quelle nach Anspruch 3, bei der der amorphe Halbleiter mit einer Menge dotiert oder legiert ist, daß er Licht in einem ausgewählten Wellenlängenbereich erzeugt.
  6. Intrinsische radioluminiszierende Lichtquelle nach Anspruch 2, bei der die amorphe Halbleitermatrix auf die Beta-Strahlung wie ein Leuchtstoff anspricht.
  7. Extrinsische radioluminiszierende Lichtquelle mit einem beta-strahlenden radioaktiven Element, das in einer amorphen Halbleitermatrix (10) eingeschlossen ist, wobei die Matrix eine Sekundärelektronenquelle bildet, die auf die Beta-Strahlung anspricht, und wobei ein Leuchtstoff (16) so angeordnet ist, daß er Sekundärelektronen von der Elektronenquelle zur Lichterzeugung auffängt.
  8. Zusammengesetzte intrinsische radioluminiszierende Lichtquelle mit einer geschichteten Struktur, die aus abwechselnden Schichten aus (a) einem amorphen Halbleiter (10), der ein eingeschlossenes beta-strahlendes radioaktives Element enthält, und (b) aus optisch reflektierendem Material (14) besteht, wobei die amorphen Halbleiterschichten vollständig von den Schichten aus dem reflektierenden Material eingeschlossen sind, abgesehen von einer Seite der Struktur, wobei in den Halbleiterschichten erzeugtes Licht in Richtung auf die eine Seite durch eine totale innere Reflexion kanalisiert wird.
  9. Zusammengesetzte intrinsische radioluminiszierende Lichtquelle nach Anspruch 8, wobei das radioaktive Element Tritium ist.
  10. Zusammengesetzte intrinsische radioluminiszierende Lichtquelle nach Anspruch 9, wobei der Halbleiter amorphes Silizium ist.
  11. Zusammengesetzte extrinsische radioluminiszierende Lichtquelle mit einer geschichteten Struktur, die aus abwechselnden lichtimitierenden Schichten (10) und Schichten aus einem optisch reflektierenden Material (14) besteht, wobei jede lichtimitierende Schicht (10) ein beta-strahlendes radioaktives Element aufweist, das in einer Halbleitermatrix eingeschlossen ist, wobei die Matrix eine Sekundärelektronenquelle bildet, die auf Beta-Strahlung anspricht und sandwichartig zwischen Leuchtstoffschichten (16) angeordnet ist, die so positioniert sind, daß sie Sekundärelektronen von der Elektronenquelle zur Lichterzeugung einfangen, und wobei jede lichtemitierende Schicht (10) vollständig durch das optisch reflektierende Material (14) eingeschlossen ist, abgesehen von einer Seite der Struktur, wobei emitiertes Licht in Richtung auf die eine Seite durch eine innere Totalreflexion kanalisiert wird.
EP91307708A 1990-09-17 1991-08-21 Radiolumineszierende Lichtquellen Expired - Lifetime EP0476845B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US07/583,209 US5118951A (en) 1990-09-17 1990-09-17 Radioluminescent light sources
US583209 1996-01-03

Publications (2)

Publication Number Publication Date
EP0476845A1 EP0476845A1 (de) 1992-03-25
EP0476845B1 true EP0476845B1 (de) 1995-03-08

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EP91307708A Expired - Lifetime EP0476845B1 (de) 1990-09-17 1991-08-21 Radiolumineszierende Lichtquellen

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US (1) US5118951A (de)
EP (1) EP0476845B1 (de)
JP (1) JP3062315B2 (de)
AT (1) ATE119707T1 (de)
CA (1) CA2049409C (de)
DE (1) DE69107939T2 (de)

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Publication number Priority date Publication date Assignee Title
IL104789A (en) * 1993-02-18 1995-12-31 Scopus Light 1990 Ltd Radioactive marker
CA2120295C (en) * 1993-04-21 1998-09-15 Nazir P. Kherani Nuclear batteries
US5721462A (en) * 1993-11-08 1998-02-24 Iowa State University Research Foundation, Inc. Nuclear battery
US5561679A (en) * 1995-04-10 1996-10-01 Ontario Hydro Radioluminescent semiconductor light source
DE19730899B4 (de) * 1997-07-18 2004-04-15 Bruker Daltonik Gmbh Ionenmobilitätsspektrometer mit einer radioaktiven β-Strahlungsquelle
DE19758512C2 (de) * 1997-07-18 2000-06-29 Bruker Saxonia Analytik Gmbh Ionenmobilitätsspektrometer
JP3570864B2 (ja) * 1997-08-08 2004-09-29 パイオニア株式会社 電子放出素子及びこれを用いた表示装置
US6665986B1 (en) * 2002-05-02 2003-12-23 Kevin Marshall Kaplan Phosphorescent paving block
US7482608B2 (en) * 2005-04-20 2009-01-27 Iso-Science Laboratories, Inc. Nuclear powered quantum dot light source
US20100289121A1 (en) * 2009-05-14 2010-11-18 Eric Hansen Chip-Level Access Control via Radioisotope Doping
US8653715B1 (en) 2011-06-30 2014-02-18 The United States Of America As Represented By The Secretary Of The Navy Radioisotope-powered energy source
JP2013058621A (ja) * 2011-09-08 2013-03-28 Advanced Power Device Research Association 半導体装置
US9581316B2 (en) 2013-01-14 2017-02-28 Cammenga Company, Llc Apparatus and method for encapsulating tritium
CN109163301A (zh) * 2018-10-18 2019-01-08 华域视觉科技(上海)有限公司 无源发光光源、制备方法及车灯

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FR2382751A1 (fr) * 1977-03-04 1978-09-29 Hanlet Jacques Structure luminescente avec source de rayonnement incorporee
US4935632A (en) * 1985-09-23 1990-06-19 Landus Inc. Luminescent concentrator light source
GB8523422D0 (en) * 1985-09-23 1985-10-30 Spectral Eng Ltd Tritium light
US4855879A (en) * 1988-08-05 1989-08-08 Quantex Corporation High-luminance radioluminescent lamp

Also Published As

Publication number Publication date
DE69107939D1 (de) 1995-04-13
JPH05107394A (ja) 1993-04-27
CA2049409A1 (en) 1992-03-18
EP0476845A1 (de) 1992-03-25
CA2049409C (en) 1994-05-10
ATE119707T1 (de) 1995-03-15
JP3062315B2 (ja) 2000-07-10
DE69107939T2 (de) 1995-11-23
US5118951A (en) 1992-06-02

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